The Effect of Physical Resistance Training on Baroreflex Sensitivity of Hypertensive Rats

Background: Baroreceptors act as regulators of blood pressure (BP); however, its sensitivity is impaired in hypertensive patients. Among the recommendations for BP reduction, exercise training has become an important adjuvant therapy in this population. However, there are many doubts about the effects of resistance exercise training in this population. Objective: To evaluate the effect of resistance exercise training on BP and baroreceptor sensitivity in spontaneously hypertensive rats (SHR). Method: Rats SHR (n = 16) and Wistar (n = 16) at 8 weeks of age, at the beginning of the experiment, were randomly divided into 4 groups: sedentary control (CS, n = 8); trained control (CT, n = 8); sedentary SHR (HS, n = 8) and trained SHR (HT, n = 8). Resistance exercise training was performed in a stairmaster-type equipment (1.1 x 0.18 m, 2 cm between the steps, 80 degrees incline) with weights attached to their tails, (5 days/week, 8 weeks). Baroreceptor reflex control of heart rate (HR) was tested by loading/unloading of baroreceptors with phenylephrine and sodium nitroprusside. Results: Resistance exercise training increased the soleus muscle mass in SHR when compared to HS (HS 0.027 +/- 0.002 g/mm and HT 0.056 +/- 0.003 g/mm). Resistance exercise training did not alter BP. On the other hand, in relation to baroreflex sensitivity, bradycardic response was improved in the TH group when compared to HS (HS -1.3 +/- 0.1 bpm/mmHg and HT -2.6 +/- 0.2 bpm/mmHg) although tachycardia response was not altered by resistance exercise (CS -3.3 +/- 0.2 bpm/mmHg, CT -3.3 +/- 0.1 bpm/mmHg, HS -1.47 +/- 0.06 bpm/mmHg and HT -1.6 +/- 0.1 bpm/mmHg). Conclusion: Resistance exercise training was able to promote improvements on baroreflex sensitivity of SHR rats, through the improvement of bradycardic response, despite not having reduced BP.